1. Field of the Invention
The present invention relates to a vibration wave motor for driving a movable member by a vibration wave and, more particularly, to a so-called circumferential opposing type vibration wave motor having a structure for converting rotary movement into linear movement.
2. Related Background Art
Various structures of a conventional vibration wave motor for rotating a movable member by utilizing a vibration wave generated by an elastic ring have been proposed, as disclosed in Japanese Patent Unexamined Publication No. 201684/1984.
In order to convert rotary movement into linear movement in a conventional vibration wave motor of this type, a mechanism for converting rotary movement into linear movement, such as a screw, a rack, a gear, and the like is required. In order to move a camera lens in the axial direction thereof, a conversion mechanism using a separate helicoid for converting rotary movement of a movable member into linear movement is required, as disclosed in Japanese Patent Unexamined Publication No. 111117/1984. However, in a conventional apparatus wherein the separate conversion mechanism is used to convert rotary movement generated by the movable member into linear movement, a large energy loss is caused and a motor output must be increased by the loss.